Fully mechanical pressure relief system

Abstract

A mechanical pressure relief system for a pressurized operating system which is suitable for high purity applications. The pressure relief system utilizes a mechanical logic switch, operable at a set point pressure, in conjunction with a pressurized actuating fluid, completely separated from the processing fluid. The system further utilizes shuttle valves to provide an additional degree of safety, with the minimization of emission of potentially highly hazardous gases, when used in the pressure relief system to prevent further inflow and outflow of processing fluid. Diversion elements are activated, with the pressure logic switch at preselected pressures, for ingress into the system of an actuating fluid. The actuating fluid serves to open venting passageways and to close processing fluid passageways until excessive pressure is relieved. When normal pressure is attained, the pressure logic switch reverses with closing of venting passageways and opening of processing fluid passageways. A belleville spring with a specific eversion pressure characteristic, operates in a fluid tight manner to direct flow of the actuating fluid to operable sites and which reverts to initial position upon pressure relief. Optional safety elements, operated by the actuating fluid, include a manual reset or controlled restart.

What is claimed is: 
     
       1. A mechanical pressure relief system for a processing system having a pressurized processing fluid flowing through processing fluid passageways, said pressure relief system comprising mechanical pressure logic switch means situated within the processing system, whereby the logic switch means is exposed to the pressurized processing fluid, said pressure relief system further comprising actuating fluid means; actuating fluid passageways, completely separate from the processing fluid passageways; and processing fluid vent valve control means, actuatable by said actuating fluid means; wherein the mechanical pressure logic switch means is activated, at a pre-determined set point pressure of the processing fluid above that of the normally pressurized processing fluid, to above access of the actuating fluid means to actuate the processing fluid vent valve control means, for venting of the processing fluid, wherein, with said venting and return of the processing system pressure to the set point pressure, the pressure logic switch means cuts off access of the actuating fluid to the processing fluid vent valve control means, thereby ending the venting and wherein said system further comprises shuttle valve control means, in operative association with a valve controlling the inlet of processing gas to the processing system, and in operative association with a valve controlling the outlet of processing gas from the processing system; wherein said shuttle valve control means is activated at the pre-determined set point pressure of the processing fluid, by the actuating fluid means, to close the valve controlling the inlet of processing fluid and to close the valve controlling outlet of the processing fluid from the processing system. 
     
     
       2. The pressure relief system of claim 1, wherein the valve controlling the inlet of processing gas and the valve controlling outlet of the processing gas from the processing system remain closed with the return of the processing gas to the set point pressure. 
     
     
       3. The pressure relief system of claim 2, wherein the shuttle valve control means comprises intentional reset means to effect opening of the valve controlling the inlet of processing gas and the valve controlling outlet of the processing gas from the processing system.